I'll try to explain it as best as possible. For every new ilv 75 Supra Primary Tool you need to trade in 3x Mastercraft Demimateria + 10x Fieldcraft III Demimateria ( and some extras, not too difficult to do )
The most efficient way to get those Demimateria is to Desynthesize the ilv 70 Artisan Spectacles. To get 1 you have to trade in 10x HQ Spicy Tomato Relish.
At Goldsmith Desynthesis lv 100.00 you now have a 100% success rate on ilv 70 gear so you won't botch an attempt.
If I'm getting 1 Mastercraft for every 10 trade ins ( 100 HQ Spicy Tomato Relish ) I will need 21x more Mastercraft for the 7 other Supra ilv 75 Primary Tools. I need to make another 2,100 HQ Spicy Tomato Relish and each requires 11x Fire shards + 10x Water Shards.
23,100 Fire shards x 90 Gil each = 2,079,000
21,000 Water Shards x 75 Gil each = 1,575,000
3,654,000 Gil worth of shards... if rates stay the same on Ultros